1. Technical Field
The present invention relates to an image recording apparatus, image recording method, and recording medium storing a program for recording an image.
2. Background Art
In image recording apparatuses, e.g., inkjet recording apparatuses, a recording head that consists of multiple driven nozzles that discharge ink droplets (ink discharging nozzles) is mounted on a carriage. Images are formed by moving (main scanning) the carriage in the direction perpendicular to the recording medium carrying direction and discharging ink droplets.
If the number of nozzles that discharge ink droplets simultaneously changes, since load to drive the nozzles (capacitance) changes too, rise time and fall time of the driving waveform changes and discharging velocity of the ink droplets becomes unstable. There then arise problems such as increasing satellites (mist) due to overshoot and undershoot in the driving waveform.
FIG. 11 is a diagram illustrating head driving waveforms for each of driven nozzles that discharge ink droplets simultaneously. In FIG. 11, the ordinate indicates head driving voltage and the abscissa indicates time.
In the driving waveforms shown in FIG. 11, the number of driven nozzles that discharge ink droplets simultaneously is small (189 nozzles) in driving waveform (1), and rise time and fall time are short (i.e., ideal waveform). By contrast, in driving waveform (2), the number of driven nozzles that discharge ink droplets simultaneously is large (756 nozzles), and rise time and fall time become long (i.e., dull waveform). This difference in waveform increases with the total number of nozzles in the recording head and with the per-nozzle load of discharging ink droplets.
To solve this issue, a technology that includes multiple driving circuits, selects a driving circuit to be used in accordance with the number of driven nozzles, and adjusts driving capability is well known. The image recording apparatus described in JP-2008-254204-A includes a driving circuit that drives a recording head that includes recording elements. In the recording head driving circuit, multiple driving circuits are connected to one recording element in parallel. The recording head driving circuit includes an output circuit block that converts voltage supplied from a power supply into driving voltage that has a predetermined waveform, a recorded data integrator that integrates the number of the recording elements based on recorded data, and a driving circuit selector that selects at least one driving circuit from the multiple driving circuits so that on resistance of the output circuit block becomes less than a predetermined value in accordance with the integrated value calculated by the recorded data integrator.
However, such an approach entails an increase in cost due to the presence of multiple driving circuits.